Test failures on unreleased sympy

To reproduce:

pip install git+https://github.com/sympy/sympy.git
py.test

Produces

FAILED pymablock/tests/test_block_diagonalization.py::test_block_diagonalize_hamiltonian_symbolic[2] - ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all().
FAILED pymablock/tests/test_block_diagonalization.py::test_input_hamiltonian_symbolic[2] - ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all().